Standard therapy for metastatic prostate cancer is androgen ablation, however, virtually all tumors become androgen-independent and the patient eventually relapses. Our long term goal is to understand the mechanisms of growth control in androgen-independent prostate cancer; such knowledge may ultimately allow the design of new therapies. We found that overexpression of transforming growth factor beta1 (TGFbeta1) in rat prostate cancer cells dramatically affected their growth in vivo and in vitro, and we found TGFbeta1 levels were higher in prostate cancer than normal prostate. We postulate that TGFbeta1 produced by prostate cancer cells is an important autocrine and paracrine regulator of prostate cancer growth. The goal of this proposal is to further test this hypothesis and to investigate the molecular mechanisms involved in these effects. Aim 1 is to investigate the role of TGFbeta1 in rat prostate cancer cell proliferation. To do this, the growth of nontransfected cells, cells stably transfected with sense TGFbeta1 cDNA, and cells stably transfected with antisense TGFbeta1 DNA will be studied in vivo and in vitro. Growth in vitro will be studied in the absence vs. presence of exogenously added TGFbeta1, or TGFbeta neutralizing antibody. These studies will be carried out using the Dunning R3327-MATLyLu, -AT2 and -G prostate cancer cell lines which form tumors in rats that differ in metastatic potential, growth rate, degree of differentiation, and sensitivity to androgen. Aim 2 is to study the molecular mechanisms of action of TGFbeta1 in prostate cancer cells. Using nontransfected and transfected MATLyLu, AT2, and G cells, we will investigate the effects of TGFbeta1 on TGFbeta receptor levels and production of other growth factors. We will also investigate the role of adenylyl cyclase and G proteins in TGFbeta1 signal transduction. Aim 3 is to study the production and processing of TGFbeta protein. Immunoblot analysis will be used to characterize the TGFbeta polypeptides that are produced and secreted by the different prostate cancer cell lines. Antibodies will be used to determine whether multiple polypeptides are produced and whether processing of the precursor is normal. Aim 4 is to study TGFbeta expression in human prostate cancer. We will analyze TGFbeta expression (mRNA levels and immunohistochemical staining) in normal human prostate and prostate cancer (different stages and grades). If TGFbeta expression is elevated in cancer, its effect on human prostate cancer growth will be evaluated by stable transfection of human prostate cancer cell lines (DU145, PC3) with TGFbeta1 cDNA, and growth of TGFbeta1- overproducing subclones in vitro and in nude mice in vivo.